Method for the use of dynamic vacuum in foundry operations



y 1965 M. SCHAIBLE ETAL 3,181,213

METHOD FOR THE USE OF DYNAMIC VACUUM IN FOUNDRY OPERATIONS Filed March 6, 1965 2 Sheets-Sheet 1 INVENTORS MICHAEL ScHAIBLE AND WAINWRIGHT Tums,

ATTORNEYS.

y 1965 M. SCHAIBLE ETAL 3,181,213

METHOD FOR THE USE OF DYNAMIC VACUUM IN FOUNDRY OPERATIONS Filed March 6, 1965 2 Sheets-Sheet 2 Fig.2a

Fig. 2d

INVENTOR. MICHAEL SCHAIBLE AND BY WAINWRIGHT Tums,

W MAIL MIE ATTORNEYS.

United States Patent 0 3,181,213 METHGD IFQR THE USE @F DYNAMEC VAQTUUM KN FQUNDRY UPERATHQNS Michael chaihlle, Huston, Mass, and Wainwright Tattle, Cincinnati, (lhio, assignors, by mesne assignments, to Altamil Corporation, Indianapolis, End, a corporation of Delaware Filed Mar. 6, 1963, Ser. No. 263,156 ll) Claims. (Cl. 22-193) This application is a continuation-impart of two pre viously filed applications. The first of these applications, Serial No. 116,743, filed June 13, 1961, entitled Apparatus and Method for the Use of Vacuum in Foundry Operations is now abandoned; the other application, Serial No. 179,960, filed March 15, 1962, entitled Automatic Mold Preparing Apparatus discloses and claims a completely automatic mold preparing machine which will successfully carry out the process of this invention.

This invention relates broadly to foundry practice and specifically to the use of a dynamic vacuum to facilitate the manipulation of molds and cores.

Both the method and apparatus of this invention have particular utility in the preparation of sand molds, including both those which are chemicall hardened by blowing with gas or the like, as well as the so-called green sand molds hardened'by a mechanical compacting operation. While the ensuing discussion will deal primarily with sand molds of the above-mentioned types,

it should be understood that this is not to be construed as a limitation on this invention.

In the simplest form, the production of molds to be used for casting requires that a moldable material be formed about a suitable pattern in a mold frame secured to the pattern, or in a flask which is separate from the pattern. The combination of a pattern and mold frame is termed a mold box. The mold box, or the pattern surrounded by a separate flask, is filled with a moldable material and hardened by compacting mechanically with a hinder, or by hardening a binder by a physical change such as drying, crystallizing, gelling or freezing, or by a chemical change such as neutralizing, or polymerizing, or a combination of methods.

In order to use the mold for casting it must be separated from the pattern. When a mold box is used, the mold is usually removed completely from the box by a number of movable extractor pins or knockouts which move through the pattern. When a pattern and flask is used, the mold is usually removed by supporting either the pattern or the flask; and, using vibration to break any adhesion, separating the pattern from the mold and flask combination mechanically or by gravity.

In the case of molds which are made very hard, with shear strength from 30 to 75 p.s.i., in order to hold accurate dimensions, and to permit deep draws with little or no draft, the mechanical or gravity method of separation without extractor pins is not satisfactory because microscopic irregularities in the pattern and/or weak sections in the mold shape prevent separation without breakage. Extractor pins located under every area of deep draw or narrow section, operating with great accuracy can accomplish the separation successfully, but the cost and difiiculty of constructing and maintaining large numbers of accurate mechanical extractor pins, springs, plates, and bushings is unfavorable; and, in addition, reduces the number and limits the configuration of pattern shapes that can be used.

In the case of molds which are of so-called green sand with compacted compressive strengths of 5 to 20 p.s.i., extractor pins cannot be used because they would merely "ice penetrate the sand. Hence, mechanical separation and/ or gravity, usually with vibration, are used.

While extraction of sand molds from the mold box presents a very important aspect of this invention, similar problems are encountered in handling sand molds in other phases of production. For example, once a mold has been extracted from its mold box, it must be transported to a subsequent station for assembly prior to pouring. It has generally been found unsatisfactory to transport a large sand mold by means of mechanical elements which grip the sides of the mold, in view of its fragile nature. And, of course, it will be understood that if the conveying apparatus is to be used to assemble mating mold halves, the conveying mechanism cannot transgress on the parting face of either mold half.

It is, therefore, a principal object of the instant invention to provide a method for handling and manipulating molds during the various phases of their production and use.

More specifically, an object of this invention is to provide a method for extracting a mold, and especially a thin, fragile, and relatively porous mold from its mold box without damage.

It is another object of this invention to provide a method of mold extraction which will eliminate costly and troublesome extractor pins or knock-outs.

It is a further object of this invention to provide a method which will permit the separation of very fragile green sand molds from patterns without using flasks to support and handle such molds.

Still a further object of this invention is the provision of a method for handling a thin mold of a large surface area which it has heretofore been impossible to handle by any means.

t is another object of the invention to provide a method for handling and transporting fragile molds without the use of flasks and without touching the parting face after being separated from the pattern, in order to avoid damage and maintain accuracy.

It is still another object of the invention to provide a method for handling molds which permits automatic conveying in such a manner that a pair of mating mold halves can be brought together or closed without requiring flasks or a friction grip on the sides of the mold halves or anything along the parting faces to interfere with closing.

It will, of course, be understood that many of the problems which are encountered in the handling of molds are also met in handling cores. For example, cores must be separated from the core box, and then transported to an assembly station. As was the case with molds, handling by separate mechanical gripping devices is unsatisfactory because of the problem of damage to the cores, and excessive complexity. It should, therefore, be apparent that this invention also applies to the manipulation of cores, and has particular utility in the automatic forming, hardening, transporting and setting of cores in a mold half.

In this connection, it should be pointed out that according to conventional practice, corernaking generally is carried out separately and independently of the mold preparing operations. Once the various mold portions and cores have been made, they must be assembled, and except in very special cases, this has heretofore been entirely a hand operation.

It is, therefore, a general object of this invention to provide a method which will coordinate the mold making and core making operations.

More specifically, it is an object of the invention to provide a method by which one or more cores are formed and hardened in a two part corebox, and subsequently ejected from one part of the corebox so that they may a. be transported and handled while still partially imbedded in the other part of the corebox.

Another object of the invention is the provision of a method which may be used to automatically eject one or more cores from one portion of the corebox, and which will operate without changes, on many different types and spacings of cores.

A further object of this invention is to provide a method by means of which a plurality of cores may be formed and transported in properly spaced relationship, so that all such cores may be set in the cavities in a mold half at the same time.

.Still another object of the invention is to provide a method by means of which one or more cores may be positioned in the cavities in a mold half more accurately than has heretofore been possible.

Another object of the invention is the provision of a method for mechanically setting cores without mold or core damage, or dislodging sand.

Numerous other objects and advantages of the method of this invention will become apparent to the skilled worker in the art as this specification proceeds.

FIGURE 1 of the accompanying drawing illustrates schematically an exemplary apparatus by means of which the method of this invention may be carried out. This particular apparatus is described in detail in the application referred to above, entitled Automatic Mold Preparing Apparatus, of which this particular application is a continuation-in-part.

FIGURES 2A-2D of the accompanying drawing shows in more detail the successive operations of the machine shown in FIGURE 1 in carrying out the extraction of a sand mold from its mold box.

As noted at the outset of this specification, the invention in its broadest aspects contemplates the use of a dynamic vacuum in the handling and manipulation of sand molds and cores. It will be understood that the phrase dynamic vacuum as used hereinafter in this application describes a continuous pressure differential created by a continuous flow of fluid (on the order of 40 to 100 cubic feet of free air per minute) through a porous medium. This flow will create a pressure difference of less than inches of water column. It will, of course, be realized that the volume of free air drawn through a sand mold will depend upon the area of the mold, its thickness, and the fineness of the sand used. In any event, the volume of air moving through the mold is given to indicate the order of magnitude thereof, and to compare the dynamic vacuum of the process of this invention with what might be called a static vacuum or low pressure region existing in a substantially sealed chamber, where the free air flow to maintain the vacuum is substantially zero (perhaps 1 cubic inch per minute free air), and the absolute pressure can be anything down to almost zero.

Briefly, in the practice of this invention, a hollow moldsupporting member is brought to bear against the exposed surface of a leveled or squeezed sand mold. Air is then continuously exhausted from the supporting member in order to maintain a subatmospheric pressure therein in spite of a large air movement through the pores of the sand mold. The sand mold will then be positively held against the supporting member by the resistance of the individual grains of sand to the continuous flow of air through the mold.

Turning now to the drawing, the apparatus schematically illustrated therein includes seven machine stations, which for convenience may be numbered 1 to 7.

Station No. 1 is the mold shooting station at which sand is shot into a mold box containing a pattern to provide a mold half. The pattern will of course have suitable vents for escape of air during mold shooting, escape of air during gassing in the case of CO sand, and the free entry of air for extraction. At Station No. 2 there is provided a transfer mechanism which carries a drag mold box and a cope mold box. These boxes consist of respectively, a mold frame and a drag mold pattern, and a mold frame and a cope mold pattern. The transfer apparatus alternately delivers an empty drag mold box and an empty mold box to the shooting station (Station No. 1), and a filled cope mold box and drag mold box to Station 3 which is the extraction station. Beyond the extraction station is Station No. 4 which is again a transfer station. Its function is to assist in extraction of both the cope and drag molds, and to transfer an extracted cope and drag to Station No. 5 in the proper position for assembly, as will be more fully described hereinafter.

In the meantime, a two part core box is being shot with sand at the core shooting station, which is Station No. 7; and, after shooting, the cores are automatically ejected from the core box top. Thereafter, the core box bottom, with the completed cores in place, is transferred by the mechanism of Station No. 6 from the core shooting Station No. 7 to the assembly Station No. 5.

All of the foregoing operations occur in a timed sequence, so that at a given time there will be at the assembly station (Station No. 5), a drag mold, a cope mold and the corebox bottom with cores therein, all properly oriented for assembly. At this station, the mold is assembled, and the completed mold may then be transferred to a discharge point for pouring.

The apparatus briefly described above carries out the entire mold preparing operation. The method of this particular invention relates specifically only to Station No. 3 through Station No. 7 of the above-described apparatus, but it is believed that the brief description of the entire apparatus will be very helpful in understanding the method of this invention.

Returning now to Station No. 2, it will be remembered that the opposite arms 10 and 11 hold respectively a cope mold box 12 and a drag mold box 13. In the position indicated in the drawings, a filled drag mold box 13 has been presented to the extraction station. At the same time it will be seen that a drag carrier 14 of Station No. 4 has been presented to Station No. 3, in a position overlying the filled drag mold box 13. The drag carrier 14 will be connected through suitable large piping to a suction blower. (The large piping and suction blower are conventional, and inasmuch as they do not per se form a part of this invention, they have not been shown in the drawings.) At this point, the hydraulic table 15 of Station No. 3 rises to bring the exposed surface of the drag in the drag mold box 13 into contact with the drag carrier 14, and the bearing portions of the face drag carrier 14 are permitted to imbed slightly in the mold surface to assist in locking the mold in place against any lateral slippage. In the case of CO sand, the mold is hardened by blowing with gas at this time. By means of the suction blower and piping referred to above, air is continuously exhausted from the drag carrier 14 so as to maintain a sub-atmospheric pressure or dynamic vacuum therein, in spite of the large air movement through the pores of the sand mold. As the hydraulic table 15 and drag mold box 13 are lowered, the drag mold 13a will be retained by the drag carrier 14, as shown in FIG- URE 2.

When a mold is extracted from the mold box, it acts as a piston with the mold frame as the cylinder. If the mold is extracted rapidly, the great increase in volume between the mold and pattern lowers the pressure in this space because atmospheric air must enter this space through the relatively restricted openings of the pattern vents, and would substantially destroy the pressure differential created by the continuous exhausting of air through the porous sand mold. Hence it is necessary to provide sufficient air at the interface between the mold and pattern to maintain the pressure differential. While it is possible to extract a mold from its mold box by a dynamic vacuum alone by withdrawing it very slowly, it is preferable to supply air at least at atmospheric pressure to this interface between the mold and pattern in order to accomplish extraction at commercially acceptable speeds. To this end, as noted before, the pattern is provided with suitable vents connected to any conventional source of air under pressure, By applying air under pressure through these pattern vents, a greater pressure diiierential can be applied to the mold, and the extraction can be as rapid as desired.

011cc the mold has been extracted from its mold box, the hydraulic table 15 of Station No. 3 may be lowered, and the mold will remain supported from the drag carrier 14. It will, of course, be understood that when the arm lb of Station No. 2 is in position over Station No. 3, the drag carrier 14- will be rotated out of position, and the cope carrier 16 will be in the position indicated in the drawing over the hydraulic table of Station No. 3. Like the drag carrier 14, the cope carrier 16 is essentially a hollow supporting member connected to a suction blower.

it will be seen that in the apparatus shown, Station No. 4 is provided with a second drag carrier MA, and a second cope carrier 16A, which are identical with the cope and drag carriers 14 and 16 just described, and which rotate about the axis of Station No. 4, so that while one set of cope and drag carriers are operating to extract e mating cope and drag molds, the other pair of carriers will be positioned at Station No. 5 for assembly of the mold.

it will also be apparent that once a cope or drag mold has been extracted by the method described above, and the empty mold box lowered by means of the hydraulic table 15, the cope or drag mold will be supported by the cope or drag carrier respectively, and may be transported thereby.

in the embodiment shown, both the cope mold box 12 and the drag mold box 13 are presented to Stations No. l and No. 3 in the same orientation. That is, when a hardened cope or drag mold is extracted at Station No. 3, they will both be oriented with their cavities facing downward. In order to assemble the mold halves, the lower or drag mold half must be inverted so that its cavities are facing up. To this end, the drag carriers 14 and 14A are provided with rollover mechanisms 17 and 17A, so that during the transportation of the drag mold from Station No. 3 to Station No. 5, it may be inverted so that its cavities are facing up. Hence by the apparatus and method just described, mating cope and drag mold halves are presented to Station No. 5 in the proper -rientation for assembly.

if the molds being formed do not require cores, the mold halves may be closed at this point. Mold closing is accomplished as follows. The hydraulic table llii carryin" a plurality of push rods 19 is raised. It will of course, be understood that the drag carriers 14 and 14A are provided with openings to accommodate the push rods 19. The push rods 19, as they are raised by the hydraulic table 118, will serve to lift the drag mold from the drag carrier, and bring it into contact with a cope mold supported by the cope carrier 16A. At this point, the suction blower communicating with the cope carrier 16A is shut off, thereby freeing the cope mold from the cope carrier 16A and permitting it to rest on the drag, and when the hydraulic table 18 is lowered, the assembled mold will drop back to the drag carrier 14A. The drag carrier may then be rotated to a discharge point, whereupon the completed mold may be removed for pouring.

As noted at the outset of this application, the method of this invention is equally applicable to the handling, transporting, and setting of cores. The formation of cores requires a two-part core box, which when joined together, forms one or more cavities designed to produce a suitable core or cores for the mold being produced at the prior stations. The core box top 2b is mounted on the core shooting machine of Station No. 7, while the core box bottom 21 is secured to the core box header 22 of Station No. 6. As briefly described earlier in this application, the core cavities in the core box are filled with sand, which is then hardened in any suitable manner to form one or more cores. If CO gas is used, the gas under pressure will be blown through suitable openings in the corebox top, and it will be understood that suitable vents are provided in the corebox bottom. To minimize gas leakage outward or air leakage inward at the parting line between the corebox parts, suction will preferably be provided through the core box header 22 to the vents in the core box bottom, so that there is a pressure gradient through the core box as a whole, varying from a positive pressure at the openings in the corebox top, to Zero pressure at the parting line between the core box parts, to a negative pressure at the vents in the core box bottom.

Before cores so formed can be handled or transported, the core box parts must be separated; and to facilitate handling by means of a dynamic vacuum as described in the case of molds, the cores must remain partially imbedded in a pre-determined one of the core box parts. The step of ejecting cores so that they will remain in one of the core box parts may also be accomplished by a pressure differential. 0n the one hand, air pressure can be applied directly to the cores through the openings in the core box top as the core box parts are separated. This method has the advantage that it is independent of the spacing of the cores, and hence no changes are needed when used with a core box having differently spaced cores.

The use of air pressure alone has the disadvantage that as soon as one core is separated from the core box top, the air pressure on the other cores will be immediately reduced, and hence ejection may not be uniform. This difriculty may be obviated by interposing a flexible diaphragm above the openings in the core box top; when air pressure is applied to this diaphragm, it will be thrust down through the openings and serve to eject the cores from the core box top. Like the use of air pressure alone, a simple diaphragm is universal, in that it can be used with any desired spacing of cores and openings in the core box.

Still a third practical alternative, and the one that provides the most positive ejective force, is to provide the diaphragm with a plurality of projections rigidly secured to a diaphragm plate and spaced to coincide with the openings in the core box top, each projection therefore pressing against an individual core. In this case, after any given core has been separated from the core box top, the entire force above the diaphragm will be applied against the core or cores remaining in the core box top.

A slight modification may be necessary in utilizing relatively large, thin core boxes. In such a case, the pressure above the core box top during ejection could cause breakage of the core box top. Therefore, it may be preferred to use a vacuum beneath the diaphragm to accomplish ejection without any net downward force on the core box top, or alternatively, vacuum may be used in addition to the pressure above the diaphragm to provide a greater force for ejection.

Once the core box parts have been separated so that all the cores remain partially imbedded in a pre-determined half of the core box, they may be securely held in place therein by means of a dynamic vacuum. That is, the core box header 2?; will be connected through suitable large piping to a suction blower. Continuously exhausting the air from the core box header, communicating with the cores through vents in the corebox bottom, will as before, maintain a sub-atmospheric pressure therein in spite of the relatively large air movement through the sand cores. Thus securely held in the core box bottom, the cores may be transported to the assembly station. It must be remembered however that at Station No. 7, the cores are projecting upwardly out of the core box bottom; and before they can be set in the drag mold which will be positioned at Station 5 with its cavities facing up, the core box bottom must be inverted. To this end, the apparatus of Station No. 6 is provided with a rollover mechanism indicated at 23, so that when presented to the assembly station, the core box bottom 21 will be inverted and the cores will project downwardly therefrom. The core box header 22 and core box bottom 21 have been shown in dotted lines at Station No. for assembly of the mold with cores.

Another aspect of this invention is what may be termed gang setting of cores. That is, it is obvious that since the cores for hollow castings are smaller than the castings themselves, a given quantity of cores can be produced in a smaller area than the same number of castings, and it is conventional to provide core boxes in which the cores are set much closer together than are the cavities in the mold itself. In the production of multiple cavity molds according to this invention, the core box is so constructed that the cores formed therein will be exactly spaced with respect to the cavities in the mold, and once proper registry has been obtained between the drag and the core box, all the cores may be set at once.

Assembling or closing the mold is accomplished in generally the same manner as described without the inclusion of cores. That is, the hydraulic table 18 and push rods 19 are raised, thereby lifting the drag mold from the drag carrier 14A, and bringing it into contact with the cores held in the core box bottom 21. The equal spacing of the cavities in the mold halves and of the cores in the core box permit all of the cores to be accurately set in the mold cavities at the same time. (The portion of the mold cavity in which the core is seated is generally known as the core print.) Preferably in the practice of this invention, the core prints in at least the drag will be made substantially the same size as the core print portion of the core itself, and when the drag mold is lifted by the hydraulic table and push rods, the cores will be forced into the core prints with a slight interference fit. The interference fit insures that the cores will not shift during mold closing or subsequent operations. This particular arrangement can most advantageously be used in the casting of elbows, Ts, and the like so arranged that one axis is perpendicular to the parting plane between the cope and drag. The core print for the portion of the core which is perpendicular to the parting plane will completely surround the core, and by virtue of the interference fit, will insure accurate alignment at all times.

At this point, the suction blower connected to the corebox header 22 is shut off, and the cores are discharged from the core box bottom. This discharge or separation of the cores from the core box bottom is satisfactorily accomplished by applying air under pressure to the corebox header and thence through the vents to the cores in the core box bottom at the same instant that the drag mold begins its descent.

The drag mold with the cores s'et therein is now lowered, and the core box bottom and core box header are moved out of position. Thereupon the table 18 and push rods 19 may once again raise the drag mold from the drag carrier, and on this stroke they will raise the drag mold into contact with the cope. Then, as described above, the suction blower connected to the cope carrier 16A is shut off, and the cope mold will then rest on the drag mold, and the assembled mold may be re-lowered and depositied on the drag carrier, and moved to a discharge position.

While this invention has been described in terms of its practice with a specific apparatus, no such limitation is intended. It will be apparent that many modifications may be made in this invention without departing from its spirit. Accordingly, no limitation is intended except insofar as set forth in the following claims. What is claimed as new, and what it is desired to secure by Letters Patent is:

1. The method of extracting a porous, hardened sand mold from its mold box and pattern, which includes the steps of applying a hollow supporting member against the exposed surface of said mold and continuously exhausting the air from said supporting member so as to maintain a sub-atmospheric pressure therein in spite of the movement of at least on the order of 40 cubic feet of free air per minute, through the pores of said mold, while permitting free access of air at atmsopheric pressure, at least, to the interface between said mold and pattern.

2. The method of transporting a porous, hardened sand mold, which includes the steps of bringing the exposed surface of said mold into contact with a hollow supportmg member and continuously exhausting the air therefrom so as to maintain a sub-atmospheric pressure therein in spite of the movement of at least on the order of 40 cubic feet of free air per minute, through the pores of said mold, whereby the resistance to air flow of the tortuous passages between the sand grains of said mold creates a force holding said mold against said supporting member.

3. The method of claim 2 wherein the exhausting of air is carried on at such a rate that said mold may be supported from said supporting member upon inversion of said supporting member.

4. The method of preparing a porous, hardened, sand cope mold and a porous, hardened sand drag mold for assembly, said molds being in their respective patterncontainingmold boxes, which includes the steps of extracting said cope mold by applying a hollow supporting member against the exposed surface of said cope mold and contlnuously exhausting the air from said supporting member so as to maintain a sub-atmospheric pressure therein in spite of the movement of at least on the order of 40 cubic feet of free air per minute, through said cope mold, while permitting free access of air at atmospheric pressure at least to the interface between said cope mold and pattern, whereby to cause said mold to adhere to said supporting member, transporting said cope mold to an assembly station, extracting said drag mold from its rnold box in the same manner as said cope mold, invertmg the supporting member holding said drag mold, transporting said inverted drag mold to said assembly station, and bringing said molds together.

5. The method of providing a porous, hardened sand core for a porous sand mold having at least one core print to receive the same, which includes the steps of providing a two part core box containing a porous, hardened, sand core, ejecting said core from one of said core box parts and simultaneously withdrawing the other core box part whereby said core remains partially imbedded in said other core box part, securing a hollow supporting member to said other core box part and continuously exhausting the air from said supporting memher so as to maintain a sub-atmospheric pressure therein in spite of the movement of at least on the order of 40 cubic feet of free air per minute, through the pores of said core, while permitting free access of air at atmospheric pressure, at least, to the exposed portion of said core, and bringing said supporting member, holding said other core box part and said core therein, to an assembly station.

6. The method of claim 5 wherein the exhausting of air is carried on at such a rate that said other core box part and said core therein may be supported from said supporting member upon inversion of said supporting member, and including the step of inverting said supporting member while bringing said supporting member to said mold.

7. The method of claim 6 including the step of seating said core in the core print of said mold.

8. The method of claim 7 including the step of discharging said core from said other core box part by supplying air under pressure to the interface between said core and said other core box part, while separating said other corebox part from said mold.

9. The method of claim 8 wherein said core print is substantially the same size as said core, said core being forced into said core print with an interference fit, whereby accurate alignment of said core in said mold is maintained.

10. The method of providing a porous, hardened sand core for a porous sand mold having at least one core print to receive the same, which includes the steps of 10 providing a two part core box having a cavity therein, securing a hollow supporting member to one of said core box parts, said member communicating with said cavity, filling said cavity with moldable material, hardening said moldable material by blowing with gas under pressure through the other of said core box parts, while simultaneously exhausting the air from said hollow supporting member, said gas under pressure and said exhausting of air from said hollow supporting member being balanced to provide substantially atmospheric pressure at the parting line between said core box parts.

References Cited by the Examiner UNITED STATES PATENTS 1,431,702 10/22 Smend et a1. 214-152 1,475,935 12/23 Coleman 22-47 2,148,084 2/39 Nock 25-120 2,435,507 2/48 Pattison 22-34 2,480,477 8/49 Jones 25-120 2,638,654 5/53 Jordan 25-120 2,733,493 2/56 Bryer 25-120 2,850,775 9/58 Northington et a1. 22-21 2,877,531 3/59 Heine 25-45 2,882,569 4/59 Blackburn et al.

2,956,319 10/60 Deakins et a1. 22-34 OTHER REFERENCES German application 1,021,287, printed Dec. 19, 1957 (K1 80a 62/20).

WILLIAM J. STEPHENSON, Primary Examiner.

20 ROBERT F. WHITE, MICHAEL V. BRINDISI,

Examiners. 

2. THE METHOD OF TRANSPORTING A POROUS, HARDENED SAND MOLD, WHICH INCLUDES THE STEPS OF BRINGING THE EXPOSED SURFACE OF SAID MOLD INTO CONTACT WITH A HOLLOW SUPPORTING MEMBER AND CONTINUOUSLY EXHAUSTING THE AIR THEREFROM SO AS TO MAINTAIN A SUB-ATMOSPHERIC PRESSURE THEREIN IN SPITE OF THE MOVEMENT OF AT LEAST ON THE ORDER OF 40 CUBIC FEET OF FREE AIR PER MINUTE, THROUGH THE PORES OF SAID MOLD, WHEREBY THE RESISTANCE TO AIR FLOW OF THE TORTUOUS PASSAGES BETWEEN THE SAND GRAINS OF SAID MOLD CREATES A FORCE HOLDING SAID MOLD AGAINST SAID SUPPORTING MEMBER. 